Radio receiver gain-control arrangement



Jan. 25, 1949. TYSON 2,460,202

RADIO RECEIVER GAIN-CONTROL ARRANGEMENT Filed April 19, 1944 l I I l {asE,

46 48 l i I 41 L M i QUENCH- FREQUENCY 1 OSCILLATOR 0 l CONTROLAMPLIFIER /oo LP /0/, 402, ms, 4

RI? AME v DETECTOR Alva 1 AMA AND 41 AUD. AMA osc M0 7' 9 P q 1- FIG. 2.

" GAIN :50 l CONTROL o I 1 I E r INVENTOR BENJAMI F. TYSO Patented Jan.25, 1949 RADIO RECEIVER GAIN -CONTROL ARRANGEMEN Benjamin F. Tyson,Bayside, N. Y., assignor, by

mesne assignments, to Hazeltine Research, Inc.,

Chicago, 111., a corporation of Illinois Application April 19, 1944,Serial No. 531,759

10 Claims.

This invention relates, in general, to arrangements for controlling thegain characteristic of a receiver and is particularly directed tocontrol arrangements for a receiver the operation of which may besuppressed or interrupted for a predetermined interval. While theinvention is subject to a variety of applications, it is especiallysuited for use in a wave-signal transpondor system and will be describedin that connection.

As used throughout this specification, the term wave-signal transpondorsystem is intended to designate a wave-signal translating systemincluding a receiver and a transmitter arranged to transmit a replysignal in response to a received interrogating signal, each such signalpreferably comprising a pulse-modulated radiant-energy signal.

In one prior transpondor arrangement, the receiver is of thesuperregenerative type having a linear mode of operation and thetransmitter is triggered, or set into operation, under the control ofthe receiver through an amplitude-selective circuit. Optimum sensitivityof such an arrangement is obtained by adjusting the receiver gain to acompromise value between that corresponding to maximum receiversensitivity and that which is necessary to assure freedomfrom-triggering the transmitter .on the quiescent signal output of thereceiver. This quiescent signal output comprises the noise-signal outputof the re ceiver which is obtained during intervals when no desiredsignal is being received. In general, the quiescent signal output has arelatively low amplitude as determined by the noise signals present inthe receiver circuit, but its amplitude varies with variations of theoperating potentials, tube characteristics and similar factors. In orderto maintain freedom from triggering the transmitter on the quiescentsignal output, it is customary to embody a gain-control arrangement inthe receiver for controlling the gain thereof to maintain the amplitudelevel of the quiescent signal output at that value required for optimumsensitivity. One such control arrangement forms the subject matter ofcopending application Serial No. 521,926, filed February 11, 1944, inthe name of John A. Hansen et a1. and assigned to the same assignee asthe present invention, now Patent No. 2,429,513, granted October 21,1947. That arrangement includes a system which rectifies a selectedportion of the quiescent signal output of the receiver to derive again-control voltage. The control voltage varies inversely withvariations in the gain characteristic of the receiver and is utilized tostabilize the receiver gain so as to maintain the amplitude of thequiescent signal output at the desired optimum value. While such acontrol arrangement is generally satisfactory, there are certainoperating conditions which require an unusual response of a gain-controlarrangement of the general type under consideration.

Consider, for example, an installation which includes not only atranspondor system but also other equipment having an operatingfrequency which is the same as or close to that of the transpondorsystem. In such a case, an undesirable interference problem isencountered when both the transpondor system and the other equipment areoperated simultaneously. To obviate this interference problem, asuppressor circuit may be included in the transpondor for disabling thereceiver thereof during intervals when it is desired to operate theother equipment. During such intervals and under such conditions, thequiescent signal output of the receiver is interrupted or substantiallydecreased. If the transpondor includes a control arrangement of the typedescribed above, the gain-control voltage increases greatly during thesuppression interval in a sense to increase greatly the receiver gain.As a consequence, when the receiver is energized at the end of thesuppression interval, the gain is so high that the amplitude of thequiescent signal output is sufficient to trigger the transmitter. Thishenomenon is termed false firing of the transmitter and is an undesiredcondition. which may be attributed to an operating limitation of thedescribed control arrangement in installations of the type underconsideration.

It is an object of the invention, therefore, to provide an improvedgain-control arrangement for controlling the gain characteristic of a receiver and which avoids the aforementioned limitation of prior artarrangements.

It is another object of the invention to provide an improved arrangementfor controlling the gain characteristics of a receiver the operation ofwhich may be suppressed or interrupted for a predetermined interval.

In accordance with the invention, a gain-control arrangement comprises awave-signal receiver having a gain characteristic, means for derivingfrom the receiver an output signal hav ing a characteristic which varieswith an operating condition of: the receiver, means having apredetermined time constant for deriving from the output signal acontrol effect, and means for utilizing the control effect to controlthe gain characteristic of the receiver. The arrangement output tiontaken in connection with the accompanying.

drawing, and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 is a schematic circuit diagram of a wave-signaltranspondor system,

embodying the present invention in a preferredv form, Fig. 2 comprisesgraphs utilized in explaining the operation of a portion of the Fig. 1arrangement, and Fig. 3 is a block diagram of a superheterodyne receiverincluding the present invention.

Referring now more particularly to Fig. 1, there is represented awave-signal tanspondor system for translating pulse-modulated signalsand including an improved control arrangement in accordance with thepresent invention. For convenience of explanation, the system isillustrated as a radio beacon adapted to transmit directionfindinginformation to inquiring aircraft. The beacon is generally similar tothat disclosed in the above-mentioned patent of John A. Hansen et al.,and corresponding components are identified by like reference numerals.

The beacon includes 'a receiver of the superregenerative type having alinear mode of operation. This receiver comprises an oscillatorincluding a vacuum tube l having anode, cathode and control electrodesand a frequency-determining circuit provided by an inductor I l and acondenser C. This condenser is represented in broken-line constructionsince it may be comprised in whole or in part of the distributedcapacitance of the inductor, the inter-electrode capacitance of theanode and control electrodes of tube Ill, and other stray capacitanceeffects associated with inductor H. The frequency-determining circuit'isdirectly coupled to the anode V electrode of tube l0 and is coupled tothe control electrode thereof through a blocking condenser 12. Thecathode circuit of the tube In includes a signal-frequency choke l3 anda cathode-bias resistor l5 by-passed, respectively, by condensers l5 andIS. A bias voltage of sufficient magnitude normally to preventoscillations is applied to the tube through a biasing circuit includingresistor M, a resistor l1 and a source of unidirectional potential,indicated +B. A source of space current is applied to a tap of inductorII, as indicated, and a quench voltage to provide superregenerativeoperation is applied to the control electrode-cathode circuit of tubefrom a quench-frequency oscillator I 8 by way of a coupling condenser l9and a choke 20. Choke is designed to isolate the oscillations generatedin the receiver from oscillator I8. The quench voltage delivered byoscillator l8. preferably has a sinusoidal wave form and a frequencywhich is low with reference to the oscillating frequency of tube 10.Also, the quench frequency is high with reference to thepulse-repetition frequencies of interrogating signals to be received bythe beacon and, preferably, such that the period corthe receiver.

responding to the quench frequency is equal to or less than the pulseduration of a received interrogating signal.

A detector system is coupled to the described frequency-determiningcircuit through a condenser 22 and constitutes means for deriving fromthe receiver an output signal having a characteristic which varies withan operating condition of This detector system includes a diode detector2| having a load circuit which consists of a resistor 23 and asignal-frequency choke 24. J

A pulse amplifier, including a vacuum tube and having an input circuitcoupled to the load circuit of detector 2| through a coupling condenser4|, applies the detected signal output of the receiver to means,comprising a unit 50, having a predetermined time constant for derivingfrom the receiver output signal a first control effect. Unit includes acontrol amplifier 5|, represented in block diagram, coupled to theoutput circuit of pulse amplifier 40 by means of a condenser 53 and aresistor 54. Control amplifier 5| preferably comprises a two-stageamplifier arranged as fully disclosed in the aforementioned patent ofJohn A. Hansen et a1. where such amplifier stages are designated byreference numerals 5| and 55. The output circuit of control amplifier 5|includes the primary circuit of a.

double-tuned transformer 58 damped by a resistor 59. Transformer 58 istuned to the quench frequency of the receiver so as to select thequench-frequency component of the detected signal output of the receiverfor rectification in a rectifying system provided by diode rectifier 6Dand its load circuit. The load circuit of rectifier 60 includes thesecondary winding of transformer 58, a resistor 61 and a by-passcondenser 62. The rectifying system has a predetermined 40 timeconstant, determined by resistor 6i and condenser 62, which is long withreference to the period of the quench frequency. The rectified signalvoltage produced across resistor Si is applied with negative polarity tothe input circuit of a direct current amplifier 63 through a lowpassfilter including series resistors 64 and 65 and a shunt capacitanceprovided by condenser 66a. Amplifier 63 is a conventional amplifierexcept that its load impedance 61 is located in the cathode circuit. Afirst control effect or voltage of adjustable magnitude is obtained froma. voltage tap 68 of impedance 6'! and is applied by Way of a resistor69 to the control electrode of receiver tube In, constituting means forutilizing the'first control effect to control the gain characteristic ofthe receiver.

The beacon also includes a unit 10 which comprises means forsubstantially decreasing the output signal of the receiver for apredetermined interval long with reference to the time constant of unit50 and means responsive to the last-named means for effectivelymaintaining the magnitude of the first-mentioned control effect within apredetermined range of values during this interval. More specifically,unit 10 comprises a suppressor circuit for applying a pulse-modulatedsuppressor signal to receiver tube Ill for the purpose of substantiallydecreasing or interrupting the output signal of the receiver for adesired predetermined interval. The suppressor circuit includes a pairof input terminals ll, 12 to which a suppressor signal, such as apositive pulse of unidirectional potential, is applied from any suitablesource (not shown). A rectifying system is coupled to these constant .byvirtue of diode 14 is applied to the transmitter tube.

input terminals thzough a coupling condenser 13 and a radio-frequencyfilter provided by resistors and 81. This rectifying system includes adiode rectifier 14 having as a load circuit resistor 15 and a parallelcombination of a resistor 16 and a condenser ll. Resistor 16 andcondenser 11 are selected of such such values that their combination inthe rectifying system provides an integra-t-ing circuit having afast-charging time and a slow-discharge time constant. The suppressorcircuit also includes an amplifier preferably having a sharp cutoircharacteristic. This amplifier consists of a vacuum tube 18 having aninput circuit coupled to integrating circuit 76, 11 and having aself-bias resistor 19 by-passed by a condenser 80. Amplifier 18 has ananode load resistor 88 and is normally biased just to cutoif through abiasing circuit provided by resistor 19, a resistor 8| and a source ofunidirectional potential, indicated +3. The output circuit of amplifier18 is coupled to the input circuit of receiver tube I through a couplingcondenser 82, a resistor 83 and signalfrequency choke 20. The outputcircuit of this amplifier is likewise coupled to a control circuit ofquench-frequency oscillator l8 by means of a condenser 84 and resistor85. Additionally, the output circuit of amplifier I8 is coupled througha condenser 81 and a resistor 86 to the input circuit of direct currentamplifier 63, this lastnamed circuit arrangement providing meansresponsive to the suppressor signal for maintaining the magnitude of thegain-control voltage derived from voltage tap 68 within a predeterminedrange of values during the effective interval of the suppressor signal,as will be described more particularly hereinafter.

The transmitter of the radio beacon comprises a regenerative oscillatorycircuit which is generally similar to that of the receiver, differingtherefrom principally in that no quench voltage mitter includes a vacuumtube having anode, cathode and control electrodes, the anode beingdirectly coupled to the above-described frequency-determining circuitwhich is common to the receiver and transmitter tubes. The controlelectrode of tube 30 is coupled to the frequencydetermining circuitthrough a blocking condenser SL The cathode circuit of tube 30 includesa signal-frequency choke 32 and a timeconstant circuit comprising aparallel arrangement of a resistor 33-and a condenser 34 for determiningthe duration of the transmitted pulses and the transmitter recoverytime. Resistor 33 is also connected in circuit with a resistor 35 and asource of unidirectional potential, indicated +3, to provide abiasingcircuit which normally holds the transmitter in a nonoscillatingcondition. I

The transmitter is coupled to the receiver through anamplitude-selective circuit including pulse amplifier and a cathodefollower 43 having an input circuit coupled to the output circult ofpulse amplifier 40 through a condenser 42. Cathode follower 43 has acathode load impedance 44 and a transmitter-control voltage developedthereacross is applied to the control electrode of tube 30 through aradio-frequency choke 45.

A single-antenna-ground system 46, utilized for both receiving andtransmitting, is magnetically coupled to the frequency-determiningcircuit of the beacon through an inductor 41. The antenna system istunable by means of an adjustable tuning condenser 48.

The transsponse to the John A. Hansen et al.

The operati n of the radio beacon, except for the function of unit 10,is completely described in the aforementioned Briefly, during quiescentoperating conditions when no signal is inter-- cepted by antenna 46,oscillations are periodically produced in thereceiver circuit under theinfiuence of the quench voltage supplied by oscillator l8; Theseoscillations are initiated by the low-amplitude noise signals present inthe receiver circuit and have a correspondingly small amplitude value.The generated oscillations are detected by detector 2|, producing acrossresistor 23 a low-amplitude quiescent output signal having an amplitudecharacteristic which varies in accordance with the gain characteristicof the receiver and the amplitude of the receiver noise signals. Thisquiescent signal output is amplified in pulse amplifier 40 and appliedto control unit 50 where the quench-frequency component is selected andapplied to rectifier 60 for rectification. The resulting rectifiedvoltage developed across resistor BI is applied with negative polarityto the input circuit of direct current amplifier 63,

Y determining the conductivity thereof and producing across its loadimpedance 6'! a gain-control voltage having a magnitude which varieswith the amplitude of the quiescent signal output of the receiver. Thecircuit parameters and operating potentials of unit 50 are so selectedthat under normal conditions of operation this control voltage isapplied to the input circuit of receiver tube In with such magnitude asto establish optimum sensitivity of the receiver circuit. Any variationin the gain of the receiver manifests itself in an amplitude variationof the quiescent signal output which, in turn, produces inversevariations of the gain-control voltage derived in unit 50 so that thegain of the receiver is maintaiied at that value required for optimumsensitiv ty.

The quiescent signal output of the receiver is also applied from pulseamplifier 40. to cathode follower 43, producing across its cathodeimpedance 44 a transmitter-control voltage. However, thetransmitter-control voltage developed in requiescent signal output hasinsufficient magnitude to overcome the bias voltage applied to tube 30by bias resistor 33. Consequently, during quiescent operating intevals,the transmitter remains blocked.

Let it be assumed now that an aircraft desiring direction-findinginformation from the beacon transmits thereto a pulse-modulatedinterrogating signal. In general, this signal has a high intensity withreference to the noise signals in the receiver circuit so that theoscillations generated in the receiver circuit in any quench cycleoccurring within the duration of a received pulse have a relatively highamplitude. During the intervals which intervene between pulses of thereceived signal, the output signal of detector 2| comprises thelow-amplitude quiescent signal mentioned above. The resulting outputsignal of the receiver, including both the high-amplitude andlow-amplitude signal components, is supplied to unit 50 which inresponse to the quench-frequency component thereof derives again-control voltage for maintaining the desired gain of the receiver,as indicated above. This output signal is also applied through pulseamplifier 40 to cathode follower 43. The transmitter-control voltagedeveloped across cathode impedance 44 in response to the copendingapplication of high-amplitude signal components derived from each.received pulse of the interrogating signal has suflicient magnitude toovercome the blocking potential normally applied totube 30 and initiateoscillations in the transmitter. Oscillations are thereupon continuouslygenerated in the transmitter until condenser 34 included in the cathodecircuit to such value as to block the tube and terminate the transmittedpulse. Therefore, in response to a received interrogating signal, thebeacon transmits a pulse-modulated reply signal having the samepulse-repetition frequency as the received signal and having a pulseduration largely determined by the selected value of condenser 34. Theinquiring aircraft is able to obtain bearing indications or otherdirection-finding information from the transmitted reply signal of thebeacon. V

In considering the operation of unit and its efiect on the describedoperation of the beacon, it will'be assumed that a pulse-modulatedsuppressor signal, having a wave form as represented by curve a of Fig.2, is applied to input terminals II, 12 for the purpose of suppressingthe operation of the beacon for a given interval of tube 30 becomescharged of time. The suppressor signal comprises a pulse ofunidirectional potential having a substantially rectangular wave formand positive polarity. This signal is rectified by rectifier 14,establishing across integrating circuit l6, 11 a signal voltage ofsaw-tooth wave form and positive polarity, as represented by curve b ofFig. 2. The signal voltage developed across integrating circuit I6, 11is applied to the input circuit of amplir,

fier I8 and is translated to the output ircuit thereof where it appearsas represented by curve 0. The signal thus derived in the output circuitof amplifier I8 is applied to receiver tube I0 and quench-frequencyoscillator I8 with negative polarity, as indicated by curve (1. Assumingthese components of the beacon to have cutoff levels represented bybroken-line curve e, the applied suppressor signal is effective to blockthe receiver tube and quench-frequency oscillator for a predeterminedinterval t. The duration of the blocking interval t is determined by,the magnitude of the suppressor signal as applied to the receiver tubeand quench-frequency oscillator and the time constant of integratingcircuit I6, 11 which is long with reference to the time conof therectifier system included in unit 50.

stantmentioned second control voltage which is applied through resistor86 to the input circuit of amplifier 63 during the suppression interval.The value of resistor 86 is so proportioned with reference to resistors83 and 85 that the gaincontrol voltage obtained at voltage tap 00 fallswithin a range of values having the following limits: (1) a value suchthat the gain of the receiver at the end ofa suppression interval issuificiently high to produce a sensitivity level as required to receivean interrogating signal, and (2) on the other hand, a value which causesthe receiver gain at the end of the suppression interval to besuiiiciently low that the quiescent signal output of the receiver has aninsumcient magnitude to trigger transmitter tube 30. At the end of thesuppression interval, the function of unit i0 is complete and the beaconis restored to its normal operating condition.

Th gain-control arrangement of the present invention, which in theillustrated embodiment of Fig. 1 comprisesunits 50 and 10. may beapplied to a superheterodyne, as distinguished from a superregenerative,receiver. The block diagram of 'Fig. 3 represents such an arrangement.The receiver of this figure comprises an antenna system I00 forsupplying received wave signals to a radio-frequency amplifier andoscillator module-'- -tor IOI, including as many stages ofradio-ireapplying to one or more of quency amplification as desired.Coupled in cascade to unit MI, in conventional manner, are anintermediate-frequency amplifier I02 and a detector -and audio-frequencyamplifier I03. As many stages of amplification as desired may beincluded in each of units I02 and I03. The signal output of the receivermay be supplied to any utilizing circuit, as indicated by the arrow I04.A gain-control system which may be similar to unit 50 of Fig. 1, has aninput circuit connected to the output circuit of intermediate-frequencyamplifier I02. An output circuit of gain-control system 50' is coupledto units IM and I02 for the tubes included in such units a controlvoltage. The voltage is used to control the amplification of thesignaltranslating stages of the receiver and thereby maintain the signalinput to the detector I03 within a relatively narrow amplitude range forDuring this blocking interval, the output signal of the receiver isinterrupted and the signal voltage across resistor SI of unit 50 fallsquickly to zero at a rate determined by the time-constant circuit GI,62. As a consequence, there is a tendency for direct current amplifier63 to become fully conductive. causing the gain-control voltage obtainedat voltage tap 68 greatly to increase in a direction to increase thegain of the receiver. However, during the blocking interval, thesuppressor signal is also utilized as a second control effect or voltageand is applied through resistor 86 to the input circuit of directcurrent amplifier 63 with negative polarity, as represented by curve d.This is equivalent to applying the suppressor signal to the circuit ofrectifier since it maintains a negative-polarity control voltage on theinput circuit of direct current amplifier 53 during the suppressioninterval to maintain the magnitude of the gain-control voltage derivedat voltage tap 68 within a predetermined range of values during thatinterval. This range of values is determined by the abovea wide range ofreceived signal intensities. A suppressor unit 10', which may begenerally similar to unit 10 of Fig. 1, has input terminals II and 12'for receiving a suppressor signal. Suitable output circuits of unit I0are coupled with units WI and I02 for selectively suppressing theoperation of the superheterodyne receiver for a given interval of time.An additional output circuit of the suppressor arrangement is coupled togain-control system 50' for maintaining the magnitude of thegain-control voltage derived in unit 50' within a predetermined range ofvalues during the effective interval of the suppressor signal. Theoperation of the Fig. 3 receiver, in translating received wave signals,is well understood in the art and need not be recited. The gain-controlsystem of unit 50' is effective to derive a control voltage from thenoise-signal output of the receiver to be utilized in maintaining thereceiver gain or noise signal at a desired predetermined level in amanner similar to that described in connection with the arrangement ofFig. 1. Likewise, unit 10 operates to control the output voltage of unit50' during suppression intervals, this operation also being as describedin connection with the Fig. 1 arrangement.

While there has been described what is at present considered to be thepreferred embodiment of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scop of the invention.

What is claimed is:

1. A gain-control arrangement comprising, a wave-signal receiver havinga gain characteristic, means for deriving from said receiver an outputsignal having a characteristic which varies with an operating conditionof said receiver, means having a predetermined time constant forderiving from said output signal a control effect, means for utilizingsaid control effect to control said gain characteristic of saidreceiver, means for substantially decreasing said out ut signal for apredetermined interval long with reference to said time constant, andmeans responsive to said lastnamed means for effectively maintaining themagnitude of said control effect within a predetermined range of valuesduring said interval.

2. A gain-control'arrangement comprising, a wave-signal receiver havinga gain characteristic, means for deriving from said receiver an outputsignal having an amplitude characteristic which varies with an operatingcondition of said receiver,

means having a predetermined time constant for deriving from said outputsignal a control eifect, means for utilizing said control effect tocontrol said gain characteristic of said receiver, means forsubstantially decreasing said output signal for a predetermined intervallong with reference to said time constant, and means responsive to saidlast-named means for effectivel maintaining the magnitude of saidcontrol effect within a predetermined range of values during saidinterval.

3. A gain-control arrangement comprising, a wave-signal receiver havinga gain characteristic, means for deriving from said receiver an outputsignal having a characteristic which varies with said gaincharacteristic, means having a predetermined time constant for derivingfrom said output signal a control effect, means for utilizing saidcontrol eifect to control said gain characteristic of said receiver,means for substantially decreasing the gain of said receiver for apredetermined interval long with reference to said time constant, andmeans responsive to said last-named means for effectively maintainingthe magnitude of said control effect within a predetermined range ofvalues during said interval.

4. A gain-control arrangement comprising, a wave-signal receiver havinga gain characteristic, means for deriving from said receiver an outputsignal having a characteristic which varies in accordance with theamplitude of the receiver noise signal, means having a predeterminedtime constant for deriving from said output signal a control effect,means for utilizing said control eifect to control said gaincharacteristic of said receiver, means for substantially decreasing saidoutput signal for a predetermined interval .long with reference to saidtime constant, and means responsive to said last-named means foreffectively maintaining the magnitude of said control effect within apredetermined range of values during said interval.

5. A gain-control arrangement comprising, a wave-signal receiver havinga gain characteristic, means for deriving from said receiver an outputsignal having a characteristic which varies said gain characteristic ofsaid receiver, means for interrupting said output signal for apredetermined interval long with reference to said time constant, andmeans responsive to said lastnamed means for eifectively maintaining themagnitude of saidcontrol effect within a predetermined range of valuesduring said interval.

6. A gain-control arrangement comprising, a wave-signal receiver havinga gain characteristic, means for deriving from said receiver an outputsignal having a characteristic which varies with an operating conditionof said receiver, means having a predetermined time constant forderiving from said output signal a control eifect, means for utilizingsaid control effect to control said gain characteristic of saidreceiver, means for supplying to said receiver a suppressor signal forsubstantially decreasing said output signal for a predetermined intervallong with reference to said time constant, and means responsive to saidsuppressor signal for effectively maintaining the magnitude of saidcontrol efiect within a predetermined range of values during saidinterval.

7. A gain-control arrangement comprising, a wave-signal receiver havinga gain characteristic, means for deriving from said receiver an.

output signal having a characteristic which varies with an operatingcondition of said receiver, means having a predetermined time constantfor deriving from said output signal a control effect, means forutilizing said control effect to control said gain characteristic ofsaid receiver, means for supplying to said receiver a pulse-modulatedsuppressor signal for substantially decreasing said output signal for apredetermined interval long with reference to said time constant, andmeans responsive to said suppressor signal for efiectively maintainingthe magnitude of said control effect within a predetermined range ofvalues during said interval. r

8. A gain-control arrangement comprising, a wave-signal receiver havinga gain characteristic, means for deriving from said receiver an outputsignal having a characteristic which varies with an operating conditionof said receiver, means having a predetermined time constant forderiving from said output signal a first control effect, means forutilizing said first control effect to control said gain characteristicof said receiver, means for substantially decreasing said output signalfor a predetermined interval long with reference to said time constant,means responsive to said last-named means for deriving a second controleffect, and means for utilizing said second control eifect to maintainthe magnitude of said first control effect within a predetermined rangeof values during said interval.

9. A gain-control arrangement comprising, a wave-signal receiver havinga gain. characteristic, means for deriving from said receiver an outputsignal having a characteristic which varies with an operating conditionof said receiver, means including a rectifying system having apredetermined time constant for deriving'from said output signal acontrol eifect, means for utilizing said control effect to control saidgain characteristic of said receiver, means for substantially decreasingsaid output signal for a predetermined interval long with reference tosaid time constant, and means responsive to said lasttained within apredetermined range of values during said interval.

10. A gain-control arrangement comprising, a

wave-signal receiver having a gain characteristic, means for derivingfrom said receiver an output signal having a characteristic which varieswith an operating condition of said receiver, means including arectifying system having a predetermined time constant for deriving fromsaid output signal a control effect, means for utilizing said controleffect to control said gain characteristic of said receiver, means forsupplying to said receiver a suppressor signal for sub- 12 timeconstant, and means for eiicctively applying said suppressor signal tosaid rectifying means to maintain the magnitude of said control eflectwithin a predetermined range of values during said interval.

BENJAMIN F. TYSON.

. REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED' STATES PATENTS

